Similar issue as the one posted here: https://forums.xamarin.com/discussion/183073/notarization-issue
I don't have this bug on Catalina or Big Sur. Only on Mojave and only when the app is notarized, the returned array when calling NetworkInterface.GetAllNetworkInterfaces() is empty. I tried adding the various client/server networking entitlements as suggested in the other thread but it didn't help.
I am using Visual Studio for Mac 8.7.6 (build 2).